The electric current used by various active semiconductor devices in a semiconductor chip are distributed through a set of electric interconnects or a power grid of the semiconductor chip. Therefore, the power grid is the power delivering structure in the semiconductor chip. A power grid may spread across different conductive levels, and may in general provide electric power or current to the various semiconductor devices using conductive wires, paths, pathways at different levels, and/or vias in crossing different levels. Currently, there are challenges to further improve the performance of the voltage (IR) drop, electro-migration (EM) performance, and routing resource of a power grid of a semiconductor chip.